Study shows GM corn not a threat to butterflies

Three years of research has show that the risk to butterflies from GM corn is negligible.

GMO Safety | Sep 21, 2011

Mechthild Schuppener of RWTH Aachen University has investigated whether the small tortoiseshell and peacock butterflies could be at risk from the cultivation of genetically modified Bt maize. After three years of research, the scientist concludes that the risk to butterflies from the Bt maize she studied is negligible. GMO Safety interviewed Mechthild Schuppener about the results of her research and has summarized the findings in a video.

The Bt maize in question produces three different Bt proteins, two of which target the European corn borer. Since the European corn borer is a moth, it was probable that other species of moth and butterfly would be sensitive to these Bt proteins as well.

Mechthild Schuppener therefore started by conducting a feeding experiment in the laboratory with butterflies she had bred hersef. The aim was to find out how sensitively the caterpillars respond when they eat pollen from Bt maize. The Bt pollen feed was found to start having an effect at doses of 200 to 300 pollen grains per cm². At these levels the caterpillars ate less. At 1000 pollen grains per cm² the mortality rate was much higher than for caterpillars fed on conventional maize pollen.

In the field, the scientist investigated how much maize pollen lands on the food plants of butterflies under natural conditions. Mechthild Schuppener set up pollen traps at various distances from the maize field, and placed a stinging nettle plant next to each one. As expected, the highest pollen quantities were found right next to the field edge, with an average of 150 pollen grains per cm² in the pollen traps, but only a fifth of this quantity on the stinging nettle leaves. The pollen concentrations that led to increased mortality among the caterpillars in the laboratory were not found in the field.

In another part of the project, two different agricultural landscapes were mapped for nests of the two butterfly species during the maize‐flowering period. It emerged that caterpillars do develop near maize fields, but that only some of them are there during the maize‐flowering period.